The present invention generally relates to throttle modulator assemblies and thermoplastic fluid direction tubes for insertion in such assemblies.
A common problem experienced in the automotive industry is the cracking of the aluminum or plastic EFI throttle modulator assemblies resulting from the high pressure required to insert steel fluid direction tubes, such as air by-pass tubes, into the assemblies. Furthermore, not all of the resulting cracks can be detected thus leaving a structural deformity and potential hazard in the automobile.
The use of steel fluid direction tubes in EFI throttle modulator assemblies has been extensive and is well known in the art. However, as mentioned above, the use of steel insertion tubes for throttle modulators in the automotive industry may cause undetectable cracking resulting from the high pressure required for insertion and retention. It is estimated that there may be a 3-5% failure rate involved as a result of pressure insertion of the steel tubes.
Another cause for concern is functional field failures due to the relative coefficients of thermal expansions between steel and aluminum or plastic. More specifically, steel expands at about half the rate of aluminum or plastic. Consequently, under high temperature conditions, the aluminum or plastic throttle modulator expands more quickly than the inserted steel tubes, causing a loss of tube retention in the body of the throttle modulator. This loss of retention at elevated temperatures can produce field failures from tubes falling out of modulator body due to the vibration encountered in automobile use.
Other problems may occur during the installation of the tubes regardless of whether they are made from steel or any other material. In particular, improper orientation and improper location of the insertion tubes often result upon installation into the throttle modulator assemblies. This problem is also known in other unrelated art areas and has resulted in the use of sealing rings, flanges or other devices to assure a tight fit. See, for example Costello U.S. Pat. No. 2,979,050 which discloses a header assembly for space heaters wherein exhaust tubes are retained within a plate by virtue of the exhaust tube's rib and flanged end and Pfeil U.S. Pat. No. 3,279,532 which discloses a heat exchanger wherein the tubes are retained in proper position within support plates by the use of an O-ring and a flared outer end. See also the U.S. Patents to Cunningham (U.S. Pat. No. 4,781,400), and Meneses (U.S. Pat. No. 2,453,669) which disclose tubular coupling assemblies having at least one annular bead or ring for facilitating the joining of a tube to the coupling. The use of an annular bead or O-ring provides uniformity for longitudinal insertion but does not always alleviate the improper orientation and location problems incurred during the installation.
Although thermoplastic tubes of various types have been used previously, as far as is known, they have never been used in the automotive industry for insertion into EFI throttle modulator assemblies. Representative of plastic tubing for other uses include the U.S. Patents to Jackson (U.S. Pat. No. 3,563,574) and Dorman (U.S. Pat. No. 2,326,292), both of which generally involve insertion of a thermoplastic tube into a metal assembly. But, neither of these patents recognize the particular problems associated with EFI throttle modulator assemblies.
Accordingly, there is a need for a thermoplastic fluid direction tube which alleviates the undetectable structural fracturing pattern associated with EFI throttle modulator assemblies. There also remains a need for a thermoplastic fluid direction tube which is easily and inexpensively manufactured and which reduces the occurrence of improper orientation and location of the tube during installation.